When the DNA sequence of the gene that codes for the peptide hormone insulin is compared in two mammals (e.g., humans and rats), most of the sequence differences are silent mutations
These far outnumber sequence differences that result in amino acid substitutions.
Why might this be?
A. Mutations are random with respect to an
organism's needs.
B. Amino acid substitutions often result in
proteins that have lost or compromised
function, and so are selected against.
C. A DNA sequence is more likely to mutate if
the change does not alter the amino acid
sequence.
D. Most amino acid substitutions result in a
beneficial phenotype that improves fitness
and results in a greater number of offspring.
E. Silent mutations occur in noncoding DNA
sequences.
B
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